Signaling



Sept. 12, 1933. w. BUSCHBECK SIGNALING Filed Nov. 12 1930 INVENTOR WERNER BUSCHBECK BY WM ATTORNEY Patented Sept. 12, 1933 SIGNAlLlNG Werner Euschbeck, Berlin, Germany, assignor to Tclefunken Gescllschaft fiir Drahtlose Tale graphic in. b. 151., Eerlin, Germany, a corporation of Germany Application November 12, 1939, Serial No. 495,053, and in Germany November 13, 1329 3 Claims.

This invention relates to a method and means for modulating or keying transmitters in which the energy flows througha plurality of electrical elements.

In a great number of cases, especially in shortwave transmitters, it is desirable, for instance, for reasons of wave constancy to modulate only a tube or tubes in the main transmitter, and to leave the frequency generator unmodulated. However, the frequency generator thus oscillating may in turn be disadvantageous, for example, for reasons of the small residual antenna current unavoidable during the keying intervals or spaces. In the case of military equipment, this residual current in the antenna constitutes a certain source of danger because of the fact that it affords a chance for the taking of bearings or tapping by outsiders, and it is inconvenient also for receivers, which are to operate in duplexfashion upon the same wave in the immediate neighborhood of the transmitter.

Now, to obviate these drawbacks the present invention discloses a method in which, by the aid retarding means, while the normal speed of telegraphing is maintained, the frequency genera tor remains unkeyed or unmodulated so that the requisite wave constancy is insured, whereas after a relatively long keying interval or space, say, for instance after three quarters of a second the frequency generator is disconnected or keyed to stop oscillation production. This insures that no residual antenna current flows during periods between messages.

As keying is resumed, the frequency generator is rendered operative simultaneously with the main transmitter, or, still better, slightly ahead of it. This is readily accomplishable if, for example, the back contact of the manual key of the main transmitter is used to control the fr quency generator keying device by way of retarding means. The back contact under ordinary working or keying conditions will not come to be fully depressed and normally will not complete a circuit. However, and even if this should happen the frequency generator will be disconnected or rendered inoperative only after a definite adjustable time interval because of the retarding means in the control circuits. As keying is re- 59 sumed, the back contact is opened first with the result that the frequency generator has started to generate oscillations before the other working contact of the key causes operation of the main transmitter.

A modulating or keying scheme operable in accordance with the present invention, along this line is shown in the accompanying drawing.

In lieu of the modulation of transmitter tubes and the frequency generator, the same method can be employed also to great advantage in connection with self-excited transmitters as soon as regular keying occurs in the antenna, While the rest of the transmitter equipment including the intermediate circuit becomes disconnected only after a relatively great time-interval or space (for instance, in self-excited crystal transmitters where keying of the entire transmitter is impracticable because of the great sluggishness of the crystal). The key signals which are liable to become a great nuisance in receivers mount- 7 ed in the neighborhood of the transmitter, especially in the case of duplex equipment, may be diminished to a tolerable limit at the same time by connecting, for instance, a resistance in the telephone circuit.

Referring to the drawing, applicants novel control circuit is shown as being applied to a transmitter comprising an antenna A connected to an amplifier B, which is in turn energized by a thermionic relay tube 2. This tube may be an amplifier, frequency multiplier, etc., in other words, any kind of a thermionic tube through which the high frequency waves to be keyed are relayed to the amplifier. The input circuits of tube 2 are connected with a translating device 4 which may include thermionic relays, amplifiers, frequency multipliers, etc. This relay forms no part of the present invention and need not be shown here. The input circuit of relay 4 is connected with the output elements of ahigh frequency generator 6 which produces oscillations determined by the frequency of the oscillations impressed from 8 on to the input circuit thereof.

In operation oscillations produced in 6 at a frequency determined by 8 are impressed on 4 and from 4. through blocking condenser 10 to the input electrodes of tube 2, andfrom tube 2 to the amplifier B, from which they are radiated at A. The signals relayed in tube 2 are modulated at keying frequency by determining the bias applied to the control electrode 12 of tube 2. When key T is closed on contact K the control grid 12 of tube 2 is connected through choking inductance 14 and resistance 16 to ground so that the tube 2 is operative and signals are sent out. The oscillation generator 6 is also operative to supply oscillations by way of 4 to tube 2 since the control electrode 20 of tube 6 is connected to ground through choking inductance 22, resistance 24 and closed contacts L and M.

The circuit arrangement, by means of which the oscillation generator 6 is rendered inoperative when keying operations cease in tube 2 for a time greater than keying intervals and is rendered operative slightly prior to the time at which 2 becomes operative when keying is again started, will now be described. In this circuit R denotes the relay provided in the grid circuit of the frequency generator valve 6 whereby the biasing potential thereof is varied. T is the key of the main transmitter tube 2 of the device by means of which the signals relayed in 2 are modulated at keying frequency, while A and 13 stand for two time-lag relays adapted to actuate the contact levers a and a and b, respectively so that the relay R in the grid circuit of the pilot tube 6 is opened only after a predetermined time interval follows the closing of the back contact 3 by means of the free end of T. W denotes a shunt resistance. By the use of two relays A and B a greater retardation is insured in the disconnection of the pilot transmitter as the manipulator key is reversed.

In operation of the transmitter and control device the contact a during keying is normally closed, as shown, the contact a is normally open, as shown,and the contact b is normally open, as

shown. i

To send out a signal impulse T is closed on contact K. The negative charge on the grid 12 of tube 2, which has been building up due to the break in the grid direct current circuit, is permitted to dissipate to ground or cathode and, since the oscillation generator 6 is operative due to the fact that contacts L and M are normally closed, a single impulse is sent out.

If the key T is moved into such a position that it completes a circuit with contact 3 the winding of relay A is short-circuited. The resistance W prevents the battery 5 from being directly shortcircuited. Whenthe winding of A becomes deener'gized normally closed contact 11 opens while 1 normally open contact a closes. This occurs after a predetermined time lag which prevents deenergizing of the winding of A during keying intervals. Opening of the contact a breaks the circuit which connects the winding of relay B with the source 5 by way of contact a and ground. The winding of relay B becomes deenergize'd and permitsnormally open contacts I) to close. Closing of the contact b places the winding of relay R in series with the battery A by way of contacts a, b and ground. Energizing of the winding of the relay R opens the contacts L and M to break the direct current grid circuit of the oscillation generator. Interruption of this grid direct current permits a high negative potential to build I up on the grid of tube 2 to stop oscillation or As has been pointed outhereinbefore, it is desirable that oscillations in 6 start before the tube 2 is again rendered operative by keying. This is insured by the fact that, when the key T is moved towards the signaling position, contact 3 is broken first. This removes the short circuit from across the winding of relay A so that A becomes deenergized. This permits contact a to return to its normally closed position and contact a to return to its normally open position. The instant a returns to its normally open position the circuit through relay R is broken and the contacts L and M close so that oscillations start in 6.

I claim:

1. In transmitting apparatus, a thermionic oscillation generator, a thermionic relay connected therewith, radiating means connected with the output circuit of said relay, a direct current circuit for biasing the control electrode of said oscillation generator to a point at which oscillations are produced, a magnetic relay having a movable element connected with a switch in said last named circuit, keying means connected with the input circuit of said relay tube, and a time lag relay having a winding in a circuit including said keying means and an armature in circuit with said magnetic relay for opening the switch in said control electrode circuit when the keying means is in the inoperative position for a predetermined time interval.

2. Transmitting means comprising, a thermionicoscillation generator, an amplifier connected therewith, means for determining the operativeness of said amplifier comprising, a direct current circuit including a key connected between the control grid of said amplifier and ground, and means for determining the operativeness of said oscillation generator comprising, a direct current circuit including normally closed contacts connected between the control grid of said oscillation generator and ground, a relay having its armature connected with the contacts in the direct current circuit of said oscillation generator, and its winding connected in an energizing circuit which includes a normally open contact cooperating with said key.

3. Signaling means comprising, an oscillation generator, an amplifier connected therewith, means for determining the operativeness of said amplifier comprising an energizing circuit including a key connected with said amplifier, and means for determining the operativeness of said oscillation generator comprising, an energizing circuit including normally closed contacts connected with said oscillation generator, a relay having its armature cooperating with the contacts in the energizing circuit of said oscillation generator and its winding connected in an energizing circuit which includes a time lag device, and a normally open contact cooperating with said key.

WERNER BUSCHBECK. 

